In his pitch to black voters, Donald Trump condemns the legacy of failed Democratic policies and sells himself by saying something like, “What do you have to lose?”

Today, I ask him the same question. What do you have to lose by trying something different at Wednesday’s debate?

Something really different. I mean humility, as in making a heart-to-heart plea for Americans to trust you with their sacred vote and pledging never to violate that trust or embarrass them.

A Hail Mary pass is necessary because Trump has failed to quell doubts about his fitness, and the game could soon be out of reach. With most polls showing Hillary Clinton building a comfortable lead, Trump’s current course means he’ll need a visitor’s pass to get into the White House.

That’s a lot of people, and Clinton is so confident she’s the front-runner that she dropped out of sight for most of the last week. It’s a defensive strategy designed to avoid mistakes.

Having surely played a role in the emergence of women claiming Trump had groped or kissed them against their will, Clinton took a break, knowing her media handmaidens would fan the flames for her. Even gaffe-prone Bubba has been lying low, hoping that being out of sight would keep his predator past out of mind.

The Clintons’ disappearing act coincided with a stepped-up speaking schedule for the best surrogates they have, President Obama and first lady Michelle Obama.

The dynamics, then, show Democrats getting ready to close the deal. Think of it like a good football team playing the Jets. The game is close for a while, but the better team slowly piles up the advantage until the result is lopsided and there’s not enough time to overcome it. Occasionally, the Jets win, but it’s always a surprise.

A winning performance would keep him in the game, while a bad performance would give him a head start on his vacation.

That’s where the race stands now. Clinton’s got a sophisticated operation for turning out the vote in the swing states, and the gears are shifting. There is even talk of a wave election that would give her victory and produce a Democratic Congress.

The third debate is shaping up as a make-or-break night for Trump. With an audience of 50 million or more, a winning performance would keep him in the game, while a bad performance would give him a head start on his vacation.

Here’s why humility must be central to his game plan.

First, it would be a surprise. Ready to rumble at the drop of an insult, Trump could benefit from a change of tone. I’m not suggesting a half-hearted apology of the sort he gave after his crude comments on a tape surfaced. Once was enough.

Voters already know she’s corrupt and dishonest, yet polls show that many who don’t like or trust her are nonetheless willing to vote for her.

My belief is that many of them, including some who remain undecided or say they will vote for a minor-party candidate, have been waiting for Trump to win them over by acting more consistently presidential, but are losing confidence that he can be anything other than a brawler and insult machine. Trump’s challenge is to earn a second look from them.

Those voters, the so-called persuadables who make up perhaps 10 percent of the electorate, must be the target of his plea. He must show them that he understands their doubts and is ready for the awesome responsibility that comes with the Oval Office. He needs to win their confidence before he can win their votes.

Call it a test of character or temperament or fitness. I call it heart, and Trump must finally reveal his.

His running mate, Mike Pence, often says, “Donald has a good heart.” His wife and children and surrogates like Rudy Giuliani and Dr. Ben Carson attest to his character and strength of purpose.

Perhaps they are right, but not enough people believe it yet. Only Trump can persuade the doubters, and Wednesday will be his last, best chance to show America he’s up to the job.

Wasting away in Blasland

There’s an uproar at City Hall over money, but to hear Mayor Bill de Blasio’s argument, it’s much ado about almost nothing.

Really, what’s $500 million among friends?

That’s the whopping chunk of taxpayer cash the mayor wants to use to fill a breach in a rebuilding program related to Hurricane Sandy. The “Build It Back” efforts blew well beyond budget, with the controller’s office calling the overruns “startling.”

The problem isn’t new, but de Blasio startled even the spendthrifts in the City Council by claiming he could just take that amount from other programs, without disrupting them. Most observers think he needs council approval because the money was approved for those programs.

Besides, as others noted, the city must be loaded if the mayor can come up with $500 million without disrupting services.

So true, which explains how de Blasio has gone on a spending spree since the day he took the job.

He’s adding so many employees that, as my colleague Steve Cuozzo points out, some city agencies are bursting at the seams. With even more hiring planned, costs have to grow.

Naturally, de Blasio never mentions cutting taxes or trimming spending. He rails against the cost of living in New York, then adds to it by blowing through cash like there’s no tomorrow.

At this rate, there will come a day when there won’t be a tomorrow. At least a solvent one.

Block that metaphor 1

From Politico, on the mood in Hillary Land: “But Clinton’s final sprint has become a joyless, nail-gnawing slog through Trump Tower’s moat of mudslinging — and the day-to-day worries of WikiLeaks’ dump of internal ­­emails from campaign chairman John Podesta’s hacked account is taking a toll.”

Block that metaphor 2

“Aides said the multimedia packages are the fruit of a carefully considered strategy after the November 2014 midterm elections to ensure that Obama could break through the rapid-fire daily news cycle and make the case for his accomplishments amid the cacophony of the 2016 campaign.”